1. Field of the Invention
This invention relates generally to an ammunition system for firearms, and more particularly to an ammunition system for muzzleloader firearms, which allows the ammunition to have a predetermined amount of propellant charge encased in a housing along with a separate muzzleloader projectile that when combined with the encased propellant charge, presents an ammunition cartridge that is significantly different than the prior art.
2. Description of Related Art
Like most early firearms, the first rifles were muzzleloading firearms. A muzzleloader is any firearm into which the projectile and usually the propellant charge is loaded from the muzzle of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the more popular modern designs of breech-loading firearms. There are generally three types of muzzleloading firearms: inline 209 primers and percussion, caplock, and flintlock muzzleloaders. Inline 209 primers and percussion muzzleloaders tend to look like most modern firearms. The inline and caplock muzzleloaders differ on where the nipple is attached. In an inline muzzleloader, the cap is in line with the hammer and the barrel. The inline has the nipple attached to the barrel at the breech and accessed by a bolt or break action. Also, the inline model has a removable breech plug, to facilitate cleaning. Caplock rifles have a side-mounted firing pin similar to the flintlock rifle, and operate and load in much the same way, but uses a more modern pre-loaded firing cap to fire the rifle. A flintlock style of muzzleloader dates back to the 17th century and features a flintlock mechanism that produces sparks when a piece of flint strikes its steel frizzen.
Loading a traditional black powder muzzleloader firearm generally involves a certain amount of complexity (as compared to the loading of modern firearms). For loose, granular powder such general steps include: a) making sure the rifle is not primed; b) making sure the rifle bore is clean of fouling and oil; c) setting a powder measure for a desired powder charge; d) pouring the powder into the measure and then into the muzzle of the rifle; and e) using a ramrod, pressing the bullet, such as a patched round ball, past the rifling and down the bore until it contacts the powder charge.
The ammunition used in muzzle loaded rifles has evolved from a projectile that is a round ball compressed in the muzzle end with a patch, to projectiles that have incorporated features of modern bullets. Within the latter category, bullet shaped projectiles can be further subdivided into those that are fired with a sabot (which replaces the patch), and projectiles that are lubricated slugs. A sabot is an encasing plastic cup that generally falls away from the projectile after it exits the gun. The sabot eliminates the need for a lubricating means and assures that there is a good seal between the projectile and the bore of the barrel.
Current muzzle loading ammunition comprises multiple parts that are combined together when loaded into a firearm. Because the various parts are separate, they are not sealed, and they use pyrotechnic materials such as black powder or black powder substitutes that tend to be hygroscopic (they tend to absorb moisture from their surroundings and in particular absorb water vapor from the atmosphere). As a result, their efficiency degrades overtime, and the propellant and resultant combustion products tend to corrode the firearm barrel and chamber.
A complete round of ammunition consists of all the components necessary for one firing of the gun. These normally include a projectile, the propellant or busting charge, and a primer that ignites the propellant. Other components such as cartridge case and fuse are also included.
For muzzleloading firearms, multiple ammunition components are loaded from the open end of the barrel. These multiple components include at least a propellant charge and projectile. The propellant charges comprise a predetermined amount of black powder, black powder substitutes, or smokeless gunpowder. The projectile typically comprises a bullet and a sabot. In some instances, the projectile and the propellant charge are inserted into the barrel as a unitary structure. Alternatively, the propellant charge is loaded separately from the projectile. In such instances, the propellant charge is loaded first into the barrel, followed by the sabot and the bullet.
Ammunition has evolved over the years, but some general terminology has remained constant, and the terms are used herein in their accepted fashion:                1. a cartridge, is a single unit of ammunition; for a modern small arms cartridge this is the combination of a bullet, propellant, primer and cartridge case in a single unit. The cartridge case is generally cylindrical in shape and includes an internal lumen. A propellant is contained within the lumen of the cartridge case. Ignition of the propellant provides the energy that propels the saboted bullet at a target;        2. a “round” is a term synonymous with a fully loaded cartridge containing a projectile, propellant, primer and casing; and        3. a “fixed round” is a round of ammunition which when stored outside of the firearm chamber prior to loading the round, has the propellant and the bullet commonly engaged to each other by direct engagement.        
Loading or charging propellants into muzzleloading guns has long presented problems. The propellant, either black powder or a substitute thereof, is normally handled in granular form (grains), with each charge being determined by measuring out a selected weight or volume of the propellant from a bulk supply, delivering it to the bore of the gun, placing a projectile in the bore, and seating the charge by ramrod into the breech. The charging of this propellant thus requires special tools and implements which must be carried to the field of use and kept readily available for re-loading. In addition, there is always the risk of improper measurement and spillage of loose powder. Other problems exist. It is difficult to obtain uniform powder compaction from load to load. It is difficult to re-load with speed and accuracy, and the use of smokeless powder, if not properly measured, could pose an additional risk.
Various forms of ammunition have been proposed for muzzle loading ammunition. Such ammunition over the years evolved from round ball projectiles to ammunition that has incorporated many of the features of modern bullets. For example, U.S. Pat. No. 7,726,245 issued on Jun. 1, 2010, titled “MUZZLELOADER AMMUNITION,” teaches a fixed round of ammunition for a muzzleloader firearm. The round has a bullet within a sabot that is engaged to a consumable cartridge case. The case is filled with propellant. The bullet is engaged to the propellant composition via the cartridge case. This “fixed round” attempts to incorporate fully modern bullet attributes. In contrast, the more typical muzzle loading ammunition comprises multiple parts which are combined together when loaded into a firearm.